WHITE.] SUMMARY OF CONCLUSIONS. 913 



One of the most surprising, as well as interesting, facts observed in 

 the stuch- of the Pottsville floras is the large element that is common 

 to the latter and to the flora described b}' Sir William Dawson from 

 the supposed middle Devonian beds at St. John, New Brunswick. In 

 fact, taking into view the entire flora of the Pottsville formation in the 

 Appalachian province, the identities in the composition of the floras 

 are so great, Avith respect to both genera and species, as to leave 

 little room for doubt that we have in the "Fern Ledges"' at St. John 

 beds of nearly the same age as the Pottsville formation in Pennsyl- 

 vania. In fact, as has been remarked in the preceding notes, the 

 characteristic forms of the St. John flora, such as Megalopteris^ 

 NeurojAerls retorquata^ AlethojJteris discrej^o/ns^ Alethojjteris ingens^ 

 Sphenopteris inlosa^ Sphenopteris Harttii^ Sphenopteris marginata^ 

 Pecopderis serrulata, Annnlarla JatifoJla^ and xVnnularia acicidnrh^ 

 as well as the numerous gymnospermous fruits, are so far identical 

 with, or obviously most intimatel}' related to, the upper Pottsville types 

 as to render it highly pro])able that a flora contemporaneous with that 

 of the Sewanee zone is present in the section along the St. John Harl)or. 



On the whole, as may already have been inferred, while recognizing 

 in the Pottsville formation a group of terranes equal in rank to 

 Lower Coal Measures, Allegheny series, etc., I not only do not favor 

 a classification which relegates the entire formation hard and fast to 

 the Upper Carboniferous, but I even anticipate a possible necessity for 

 its permanent division into two groups, the lower of which may even- 

 tuallv perhaps be referred to the Lower Carboniferous. From the 

 paleobotanic standpoint the Pottsville formation is the beginning of 

 the Mesocarboniferous. 



SUMMARY OF COXCI^ITSIO^STS. 



1. The Pottsville formation in the Southern Anthracite field is com- 

 posed chiefly of massive conglomerates and conglomeratic sandstones 

 of varying composition, the lower terranes being somewhat hetero- 

 geneous and irregular, the upper generalh' more uniform and persist- 

 ent, with better assorting of materials. The coals (Lykens), locally 

 of great economic importance, exhibit the general variability of the 

 formation, though they sometimes appear to extend over relatively 

 large areas. 



2. In the Schuylkill region the passage from the Mauch Chunk (XI) to 

 the Pottsville (XII) is by a transition of heterogeneous conglomerates, 

 intercalated in red and green shales, the proportion of sandstones 

 increasing to the top of the red shales, which are later represented by 

 red and green argillaceous materials washed into the soft but more 

 distinctly arenaceous conglomerates and bowlder beds of the lower 

 portion of the Pottsville. 



20 GEOL, PT 2 58 



